Implanted medical devices are of increasing interest for a wide variety of medical applications. Providing power to implanted medical devices has been performed in various ways. For example, power can be provided to implanted medical devices using RF (radio frequency) radiation or inductive coupling. Another approach is ultrasonic power transmission, which is expected to provide better performance than electromagnetic power transmission for implanted devices in some cases. US 2014/0336474 provides examples of ultrasonic power transmission, and is hereby incorporated by reference in its entirety.
However, the design considerations for efficient power transfer in an ultrasonic power transmission system are substantially different from those that arise in connection with electromagnetic power transmission for implanted devices. Therefore, design approaches suitable for providing efficient electromagnetic power transmission to implanted devices aren't applicable to ultrasonically powered implanted devices. Accordingly, it would be an advance in the art to provide improved ultrasonic powering of implanted devices.